639776961 has 14 divisors (see below), whose sum is σ = 959227730. Its totient is φ = 426517488.

The previous prime is 639776923. The next prime is 639776971. The reversal of 639776961 is 169677936.

It can be written as a sum of positive squares in only one way, i.e., 490179600 + 149597361 = 22140^2 + 12231^2 .

It is not a de Polignac number, because 639776961 - 2¹⁴ = 639760577 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 639776898 and 639776907.

It is not an unprimeable number, because it can be changed into a prime (639776971) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 13 ways as a sum of consecutive naturals, for example, 438076 + ... + 439533.

Almost surely, 2^639776961 is an apocalyptic number.

It is an amenable number.

639776961 is a deficient number, since it is larger than the sum of its proper divisors (319450769).

639776961 is an frugal number, since it uses more digits than its factorization.

639776961 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 877627 (or 877612 counting only the distinct ones).

The product of its digits is 2571912, while the sum is 54.

The square root of 639776961 is about 25293.8127019238. The cubic root of 639776961 is about 861.6737554315.

The spelling of 639776961 in words is "six hundred thirty-nine million, seven hundred seventy-six thousand, nine hundred sixty-one".